TWI422613B - Process for preparing polytetrahydrofuran or tetrahydrofuran copolymers - Google Patents

Abstract

The present invention relates to a process for preparing polytetrahydrofuran or tetrahydrofuran copolymers by polymerization of tetrahydrofuran in the presence of a telogen and/or a comonomer over a fixed bed of an acid catalyst, in which the temperature of the polymerization mixture increases in the direction of flow through the catalyst bed.

Description

Method for preparing polytetrahydrofuran or tetrahydrofuran copolymer

The present invention relates to a process for preparing a polytetrahydrofuran or tetrahydrofuran copolymer by polymerizing tetrahydrofuran via a fixed bed of an acid catalyst in the presence of a telogen and/or a comonomer, wherein the temperature of the polymerization mixture flows through the catalyst bed. The direction is raised.

Polytetrahydrofuran (hereinafter also referred to as "PTHF"), also known as polyoxybutylene butyl diol, is a common intermediate in the plastics and synthetic fiber industries, and is especially useful for the preparation of polyurethanes, A diol component of a polyester and a polyamide elastomer. In addition, polytetrahydrofuran (as with certain derivatives thereof) is a valuable adjuvant in a variety of fields, for example as a dispersant or for deinking of waste paper.

PTHF is usually prepared industrially by polymerizing tetrahydrofuran (hereinafter referred to as "THF") via a suitable catalyst in the presence of a specific reagent (chain terminating reagent or "telomer"), and the addition of such reagents makes it possible The chain length of the polymer chain is controlled and the average molecular weight can be set for this purpose. This control is achieved by the choice of the type and amount of telogen. Other functional groups can be introduced at one or both ends of the polymer chain by selecting a suitable telogen.

Thus, for example, the use of a carboxylic acid or a carboxylic anhydride as a telogen makes it possible to produce a monoester or diester of PTHF. PTHF itself is formed only after subsequent hydrolysis or transesterification. Therefore, this preparation is referred to as a two-stage PTHF process. PTHF can also be obtained in a single stage by using water, 1,4-butanediol or low molecular weight PTHF as a telogen by polymerizing THF via an acid catalyst.

Other telogens not only act as chain termination reagents, but are also incorporated into the growing polymer chain of PTHF. It not only has the function of a telogen, but also acts as a comonomer and can therefore likewise be designated as a telogen and a comonomer. Examples of such comonomers are telomers having two hydroxyl groups, such as glycols. These diols can be, for example, ethylene glycol, propylene glycol, butylene glycol, 1,3-propanediol, 1,4-butanediol, 2-butyne-1,4-diol, 2,2-di Methyl-1,3-propanediol, 1,6-hexanediol or low molecular weight PTHF.

Other suitable comonomers are cyclic ethers, preferably three, four and five membered rings, such as 1,2-alkylene oxides (eg, ethylene oxide or propylene oxide), oxetane, Substituted oxetane (such as 3,3-dimethyloxetane) and THF derived from 3-methyltetrahydrofuran, 3,3-dimethyltetrahydrofuran or 3,4-dimethyltetrahydrofuran Things.

In addition to water, 1,4-butanediol and low molecular weight PTHF, the use of such comonomers or telogens results in the preparation of tetrahydrofuran copolymers (hereinafter referred to as THF copolymers) and in this way makes it possible to chemically The PTHF was modified.

Industrially, the two-stage process described above is primarily employed, wherein, for example, THF is polymerized in the presence of a generally heterogeneous (i.e., mostly insoluble) catalyst, first forming a polytetrahydrofuran ester which is subsequently hydrolyzed to PTHF. This THF polymerization form generally achieves a higher THF conversion than the single stage process.

In addition to the catalytic efficiency of the heterogeneous catalyst, other reaction parameters and their interaction with the selected catalyst have a critical impact on the polymerization results, especially in conversion, yield, and molecular weight distribution such as color number and polytetrahydrofuran or tetrahydrofuran copolymer. Product nature.

In order to set the narrow molecular weight distribution of the polymer in a desired manner, according to JP B 10-025340, the key point is to keep the reaction temperature constant during the entire polymerization reaction via the heteropolyacid.

In contrast, US-A 4 510 333 and DE-A 42 05 984 teach to avoid homogenization of a catalyst such as fluorosulfonic acid (i.e., a catalyst which is mostly soluble in the reaction mixture) and via, for example, bleaching earth. The color number problem caused by the heterogeneous catalyst, and in order to set the narrow molecular weight distribution, it is preferred to cause the reaction temperature to rapidly decrease during the polymerization process.

EP-A 0 051 499 discloses the polymerization of PTHF via homogenization via fluorosulfonic acid or fuming sulfonic acid as a catalyst, and the process is divided into two steps. The first step occurs at a temperature in the range of -30 ° C to +10 ° C, and the second step occurs in a second stirred vessel at a temperature above 10 to 40 ° C above the above temperature. In this way, an increase in conversion can be achieved with high product purity. However, the disadvantage is that when the process is put into industrial practice, it is necessary to use two stirred reactors, high implementation costs and complicated separation operations (this is common in polymerization via homogenous catalysts).

Starting from this prior art, it is an object of the present invention to provide a process by which a polytetrahydrofuran and/or tetrahydrofuran copolymer having a narrow average molecular weight distribution can be economically produced at a good conversion rate and a low color number.

At present, we have found a process for preparing a polytetrahydrofuran or tetrahydrofuran copolymer by polymerizing tetrahydrofuran via a fixed bed of an acid catalyst in the presence of a telogen and/or a comonomer, wherein the temperature of the polymerization mixture flows through the catalyst bed. The direction is raised.

The fixed catalyst bed can be located in one or more interconnected fixed bed reactors (e.g., tubular reactors) known per se. The polymerization is preferably carried out in a fixed bed reactor.

The polymerization is usually carried out at a temperature of from 0 to 80 ° C, preferably from 25 ° C to the boiling point of THF. For the purposes of the present invention, the reaction temperature is the corresponding temperature of the polymerization mixture. The temperature (reaction temperature) of the polymerization mixture at the beginning of the catalyst bed is from 0 to 50 ° C, preferably from 25 to 45 ° C. At the end of the fixed bed, the temperature according to the invention is from 30 to 80 ° C, preferably from 35 to 55 ° C.

According to the invention, the temperature rise is at least 0.1 ° C per meter of catalyst bed, preferably 0.2 ° C per meter of catalyst bed, and particularly preferably at least 0.3 ° C per meter of catalyst bed, while the temperature rise can be continuous Or in at least two steps, preferably in two, three, four or five steps. The temperature rise preferably occurs gradually with a temperature difference of 1 ° C, preferably 2.5 ° C. The temperature rise should not exceed 5 ° C per meter of catalyst bed.

The temperature in the reactor can be raised by using a heating or cooling device known per se and customary in the industry, together with an appropriate measuring device (e.g. thermocouple) for the local temperature of the polymerization mixture. Process heaters can also be used to achieve heating.

The pressure applied is generally not critical to the results of the polymerization, which is why the polymerization is typically carried out at atmospheric pressure or at the autogenous pressure of the polymerization system. The exception is the copolymerization of THF with a volatile 1,2-alkylene oxide, which is advantageously carried out under superatmospheric pressure. The pressure is usually from 0.1 to 20 bar, preferably from 0.5 to 2 bar.

The process of the present invention makes it possible to obtain PTHF and THF copolymers having a narrow molecular weight distribution with a high degree of product conversion at a high degree of product conversion. Improved use of telogens and/or comonomers contributes to the economical use of raw materials and leads to economic processes.

In the process of the invention for the preparation of PTHF and THF copolymers, THF is passed in a first step by means of an acid, preferably a heterogeneous catalyst, preferably in the presence of acetic anhydride and, if appropriate, a comonomer. Polymerization to prepare monoesters and/or diesters of PTHF or THF copolymers.

Suitable catalysts are, for example, bleaching earth-based catalysts as described, for example, in DE-A 1 226 560. Bleaching earth (especially active montmorillonite) can be used as a shaped body in a fixed bed or in a suspension.

Further, a catalyst based on a mixed metal oxide (particularly a mixed metal oxide of a Group 3, Group 4, Group 13, and Group 14 element of the periodic table) is known to be used for polymerizing THF. Thus, JP-A 04-306 228 describes the polymerization of THF in the presence of a carboxylic anhydride via a mixed metal oxide comprising a metal oxide of the formula M _x O _y (wherein the integer values of x and y are in the range of 1-3). Examples mentioned are Al ₂ O ₃ -SiO ₂ , SiO ₂ -TiO ₂ , SiO ₂ -ZrO ₂ and TiO ₂ -ZrO ₂ . Heteropolyacids, especially H ₃ PW ₁₂ O ₄₀ and H ₃ PMo ₁₂ O _40, can be used as the supported catalyst, but are preferably in the form of no load.

No. 5,208,385 discloses a catalyst based on an amorphous mixed cerium aluminum oxide. Mixed oxidation based on SnO ₂ /SiO ₂ , Ga ₂ O ₃ /SiO ₂ , Fe ₂ O ₃ /SiO ₂ , In ₂ O ₃ /SiO ₂ , Ta ₂ O ₅ /SiO ₂ and HfO ₂ /SiO _{2 is also known} . Things. The above catalyst is preferably prepared by a coprecipitation method/sol-gel method. A supported catalyst is disclosed in DE-A 44 33 606, in which tungsten oxide or molybdenum oxide is applied to, for example, ZrO ₂ , TiO ₂ , HfO ₂ , Y ₂ O ₃ , Fe ₂ O ₃ , Al ₂ O ₃ , SnO ₂ , SiO ₂ or ZnO. Furthermore, ZrO ₂ /SiO ₂ catalysts are recommended in which the support has an alkali metal concentration of less than 5000 ppm.

Catalysts based on acid ion exchangers are described in US 4,120,903 for the polymerization of THF in the presence of acetic anhydride, the catalyst being in particular comprising alpha-fluorosulfonic acid (eg Nafion) ) a polymer. Catalysts comprising a metal and a perfluoroalkylsulfonic acid anion are also suitable for the polymerization of THF.

In addition, as disclosed in, for example, WO 94/05719, WO 96/23833, WO 98/51729, WO 99/12992, and DE-A 195 134 93, clay minerals are also considered to be polymerization catalysts when properly activated. . Zeolites are also suitable as catalysts and are described, for example, in DE-A 43 16 138. Finally, sulfated zirconia, sulfated alumina, supported heteropolyacids and supported ammonium hydrogen fluoride (NH ₄ F ^* HF) or antimony pentafluoride are also considered suitable polymerization catalysts. The process of the invention is preferably carried out using activated bleaching earth.

For example, it is possible to dry the catalyst as a pretreatment of the catalyst by means of a gas heated to 80 to 200 ° C, preferably 100 to 180 ° C, such as air or nitrogen.

In order to avoid the formation of peroxy ethers, it is advantageous to carry out the polymerization under an inert atmosphere. For example, it is possible to use nitrogen, carbon dioxide or a rare gas as the inert gas, preferably nitrogen.

The process can be carried out batchwise or continuously, but it is preferred to operate the process continuously for economic reasons.

Since the telogen causes chain termination, the average molecular weight of the polymer to be prepared can be controlled via the amount of telogen used. Suitable telogens are C ₂ -C ₁₂ carboxylic anhydrides and/or mixtures of protic acids with C ₂ -C ₁₂ carboxylic anhydrides. The protic acid is preferably an organic or inorganic acid which is soluble in the reaction system. Examples are C ₂ -C ₁₂ carboxylic acids such as acetic acid and sulfonic acids, sulfuric acid, hydrochloric acid, phosphoric acid. Preferably, acetic anhydride and/or acetic acid are used. To this end, in the first step (i.e., polymerization), monoesters and diesters of PTHF or THF copolymers are formed.

The concentration of acetic anhydride used as a telogen in the feed to the polymerization reactor is from 0.03 to 30 mol%, preferably from 0.05 to 20 mol%, particularly preferably from 0.1 to 10 mol%, based on the THF used. . If acetic acid is additionally used, the molar ratio in the feed for the polymerization being carried out is usually in the range from 1:20 to 1:20000 based on the acetic anhydride used.

The monoesters and diesters of the THF copolymer can be prepared by additionally using a ring-opening polymerizable cyclic ether as a comonomer, preferably a three-membered, four-membered, and five-membered ring, such as 1,2- An alkylene oxide (for example, ethylene oxide or propylene oxide), an oxetane, a substituted oxetane (such as 3,3-dimethyloxetane), a THF derivative (2) -Methyltetrahydrofuran or 3-methyltetrahydrofuran), of which 2-methyltetrahydrofuran or 3-methyltetrahydrofuran is particularly preferred.

It is likewise possible to use C ₂ -C ₁₂ diols as comonomers. These diols can be, for example, ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, 1,3-propanediol, 2-butyne-1,4-diol, 1,6-hexanediol or Low molecular weight PTHF. Other suitable comonomers are cyclic ethers such as, for example, ethylene oxide or propylene oxide 1,2-alkylene oxide, 2-methyltetrahydrofuran or 3-methyltetrahydrofuran.

In the fixed bed mode of operation according to the present invention, the polymerization reactor can be operated in a upflow mode, even if the reaction mixture is transported from the bottom up; or the following flow mode operation, even if the reaction mixture passes through the reactor from top to bottom . The feed comprising THF and the telogen and/or comonomer is continuously fed into the polymerization reactor while the space velocity via the catalyst is from 0.01 to 2.0 kg of THF / (1 ^* h), preferably from 0.02 to 1.0 kg of THF / (1 ^{* h)} and particularly preferably 0.04 to 0.5 kg of THF / (1 ^{* h).}

In addition, the polymerization reactor can be operated in a single pass, i.e., without product recycle; or in a recycle mode, even if a portion of the polymerization mixture remaining in the reactor is recycled. In the recycle mode, the ratio of recycled material to feed is less than or equal to 150:1, preferably less than 100:1 and particularly preferably less than 60:1.

By means of this method, monoesters and/or diesters of PTHF or THF copolymers having an average molecular weight of from 250 to 10 000 Daltons can be prepared in a targeted manner, depending on the level of telogen in the polymerization mixture. Preferably, the corresponding PTHF ester having an average molecular weight of from 500 to 5000 Daltons, particularly preferably from 650 to 4000 Daltons, is prepared by means of the process of the invention. In the present patent application, the term "average molecular weight""average molar mass" refers to a polymer or a number-average molecular weight M _n, which line (e.g.) determined according to DIN 53 240 by means of a wet chemical assay OH number .

The THF-containing output from the polymerization stage was filtered to retain the trace polymerization catalyst and then transferred to remove the THF by distillation. However, it is also possible to first separate unreacted THF and then remove the catalyst residue from the remaining PTHF monoester or diester by filtration. The second method is preferred. A bed filter conventionally used in the industry is used as a filtering device.

The ester group in the polymer obtained in this way must be converted in the second step. One conventional method is to react with a lower alcohol by initiation with a basic catalyst. The transesterification of a basic catalyst is known from the prior art and is described, for example, in DE-A 101 20 801 and DE-A 197 42 342. Methanol is preferably used as the lower alcohol and sodium methoxide is used as the effective transesterification catalyst.

The polymers obtained can be used in combination with organic isocyanates in a manner known per se to produce polyurethanes and polyurethanes, in particular for the preparation of thermoplastic urethanes, elastic rayon ( Spandex), thermoplastic ether ester or copolyether decylamine. Accordingly, the present invention further provides the use of a polytetrahydrofuran or tetrahydrofuran copolymer prepared by the process of the present invention for the preparation of a polyurethane urethane polymer or a polyurethane urethane polymer, such urethanes Polymer or polyurethane urea polymers are, for example, for the production of elastic fibers (including spandex or spandex), thermoplastic polyurethanes (TPU) or polyurethanes. Required for casting elastomers.

Here, the PTHF or THF copolymer is first reacted with an excess of the organic diisocyanate in a manner known per se, and then reacted with an organic diamine, as described, for example, in JP-A 07-278 246.

The invention is illustrated by the following examples.

Instance Molecular weight determination

By measuring the hydroxyl number of PTMEG to determine the number average molecular weight in the form of an average molecular weight M _n, which is defined as the mass of all PTHF molecules divided by its molar amount. The hydroxyl number is the amount of potassium hydroxide (mg) which is equivalent to the amount of acetic acid to which 1 g of the substance is acetylated. The number of hydroxyl groups is determined by the esterification of the hydroxyl groups present by means of excess acetic anhydride.

H-[O(CH ₂ ) ₄ ] _n -OH+(CH ₃ CO) ₂ → CH ₃ CO-[O(CH ₂ ) ₄ ] _n -O-COCH ₃ +H ₂ O

After the reaction, excess acetic anhydride was hydrolyzed with water according to the following reaction equation: (CH ₃ CO) ₂ O + H ₂ O → 2 CH ₃ COOH, and acetic acid was back-titrated with sodium hydroxide.

Determination of evaporation residue

The evaporation residue is a non-volatile material in a PTHF or PTHF ester/low boiler mixture as determined under specified conditions and is used as a measure of yield. For the determination of ER, the sample was evaporated at 145 ° C for 30 minutes under atmospheric pressure and evaporated in an evaporation flask for 30 minutes at the same temperature and under a reduced pressure of less than 1 mbar. Calculate the evaporation residue according to the following formula: Here, ER = evaporation residue, mass concentration according to DIN 1310, g/100 gm ₁ = mass of the evaporation flask plus sample, gm ₂ = mass of evaporation flask plus evaporation residue, conversion factor of g 100 = g to 100 g

method

To determine the evaporation residue, the previously weighed sample was treated with a rotary evaporator at 145 ° C and atmospheric pressure for 1 hour, and then treated at 0.1 to 0.2 mbar for 1 hour at the same temperature and weighed again. Evaporation residues were obtained as a percentage by weight of the initial value.

Determination of color number

The solvent-free and untreated polymer was measured by a liquid color measuring device LICO 200 from Dr. Lange. Use accurate cuvette No. 100-QS (path length: 50 mm from Helma).

Example 1

Self-bleaching soil (from S The K10 powder of d-Chemie) produced an extrudate of 1.5 mm average diameter and was immediately dried at 150 ° C prior to use. 200 ml (130 g) of the dried catalyst extrudate was introduced into each of two glass reaction tubes (inner internal diameter: 3 cm, effective length: 30 cm) connected in series and each having a heat-stable cooling tube. A catalyst bed having a total effective length of 60 cm was obtained for this purpose. Adjusting the temperature of the inlet of the first reaction tube (i.e., at the beginning of the catalyst bed) (P1) and the outlet of the second reaction tube (i.e., at the end of the catalyst bed) (P2) by means of a separation thermostat temperature. The temperature rise in the direction of flowing through the catalyst bed was set to 2.46 ° C per 60 cm of catalyst bed. The reactor was filled with a polymerization mixture of THF and 3.5% acetic anhydride at the inlet of the first reaction tube at 35 °C. The polymerization mixture was continuously circulated via a reaction apparatus by means of a pump, for which an additional 30 g/h of the polymerization mixture was introduced into the reactor at a constant recycle ratio:feed ratio of 15:1 while taking the same amount of product from the process. mixture. For the analysis of the product, the volatile component of the reaction product mixture (i.e., substantially unreacted THF and acetic anhydride) was first evaporated under reduced pressure at 70 ° C / 30 mbar, followed by evaporation under reduced pressure at 170 ° C / 0.3 mbar. And the polymer residue was analyzed. The results are summarized in Table 1.

Comparative example

The tubular reactor connected in series was filled with a catalyst in a manner similar to that of Example 1 of the present invention. Unlike the examples of the present invention, the temperature rise in the direction of flowing through the catalyst bed is not set. The reactor was filled with a polymerization mixture of THF and 3.5% acetic anhydride at the inlet of the first reaction tube at 35 °C. The polymerization mixture was continuously circulated via a reaction apparatus by means of a pump, for which an additional 30 g/h of the polymerization mixture was introduced into the reactor at a constant recycle ratio:feed ratio of 15:1 while taking the same amount of product from the process. mixture. For the analysis of the product, the volatile component of the reaction product mixture (i.e., substantially unreacted THF and acetic anhydride) was first evaporated under reduced pressure at 70 ° C / 30 mbar, followed by evaporation under reduced pressure at 170 ° C / 0.3 mbar. And the polymer residue was analyzed. The results are summarized in Table 1.

Claims (10)

A process for preparing a polytetrahydrofuran or tetrahydrofuran copolymer by polymerizing tetrahydrofuran via a fixed bed of an acid catalyst in the presence of a telogen and/or a comonomer, wherein the temperature of the polymerization mixture flows through the catalyst bed The direction is raised. The method of claim 1, wherein the temperature of the polymerization mixture is from 0 to 50 ° C at the beginning of the catalyst bed, and the temperature of the polymerization mixture is from 30 to 80 ° C at the end of the catalyst bed. The method of claim 1 or 2, wherein the increase in temperature in the direction of flowing through the catalyst bed is continuous or stepwise. The method of claim 1 or 2, wherein the catalyst bed is in one or more reactors. The method of claim 1 or 2 wherein the temperature increase in the direction of flow through the catalyst bed is at least 0.1 ° C per meter of catalyst bed. The method of claim 1 or 2 wherein the temperature increase in the direction of flow through the catalyst bed is at least 0.2 ° C per meter of catalyst bed. The method of claim 1 or 2 wherein the temperature increase in the direction of flow through the catalyst bed is at least 0.3 ° C per meter of catalyst bed. The method of claim 1 or 2, wherein the catalyst is selected from the group consisting of Fuller's earth, mixed metal oxides of Group 3, Group 4, Group 13 and Group 14 elements of the Periodic Table of the Elements, supported tungsten oxide or oxidized Molybdenum, acid ion exchanger, zeolite and/or sulfated zirconia. A use of a polytetrahydrofuran or tetrahydrofuran copolymer prepared by the method of any one of claims 1 to 8 for the preparation of a polyaminocarboxylic acid Ester urea polymer. The use of claim 9, wherein the polytetrahydrofuran or tetrahydrofuran copolymer prepared by the method of any one of claims 1 to 6 is used for preparing a thermoplastic polyurethane, a spandex, a thermoplastic ether ester. Or a total of polyether amide.